TDA7540B STMicroelectronics, TDA7540B Datasheet - Page 37

• Manufacturer Part Number: TDA7540B
• Manufacturer: STMicroelectronics

Specifications of TDA7540B

• Case: TQFP
• Dc: 06+
• Lead Free Status / Rohs Status: Compliant

DOCUMENT CD00108485
Copyright STMicroelectronics
TDA7540B
4.4.2
REVISION 1.0
Inlock detector
Switching the chargepump in low current mode can be done either via software or
automatically by the inlock detector, by setting bit LDENA to "1".
After reaching a phase difference about lower than 40nsec the chargepump is forced in low
current mode. A new PLL divider alternation by I
high current mode.
Low noise CMOS op-amp
An internal voltage divider at pin VREF2 connects the positive input of the low noise op-
amp. The charge pump output connects the negative input. This internal amplifier in
cooperation with external components can provide an active filter. The negative input is
switchable to three input pins, to increase the flexibility in application. This feature allows two
separate active filters for different applications.
While the high current mode is activated LPHC output is switched on.
IF counter block
The aim of IF counter is to measure the intermediate frequency of the tuner for AM and FM
mode. The input signal for FM and AM upconversion is the same 10.7MHz IF level after
limiter. AM 450KHz signal is coming from narrow filtered IF2 before demodulation. A switch
controlled by IF counter mode (IFCM) is choosing the input signal for IF counter.
The grade of integration is adjustable by eight different measuring cycle times. The
tolerance of the accepted count value is adjustable, to reach an optimum compromise for
search speed and precision of the evaluation.
The IF-counter mode
The IF counter works in 3 modes controlled by IFCM register.
Sampling timer
A sampling timer generates the gate signal for the main counter. The basically sampling
time are in FM mode 6.25kHz (t
followed by an asynchronous divider to generate several sampling times.
Intermediate frequency main counter
This counter is a 11 - 21-bit synchronous autoreload down counter. Five bits (CF) are
programmable to have the possibility for an adjust to the centre frequency of the IF-filter.
The counter length is automatic adjusted to the chosen sampling time and the counter mode
(FM, AM-UPC, AM).
At the start the counter will be loaded with a defined value which is an equivalent to the
divider value (t
If a correct frequency is applied to the IF counter frequency input at the end of the sampling
time the main counter is changing its state from 0h to 1FFFFFh.
Sample
x f
IF
).
TIM
COMPANY INTERNAL
=160
ACTIVE
µ
s) and in AM mode 1kHz (t
2
C-Bus will switch the chargepump in the
Unauthorized reproduction and communication strictly prohibited
Functional description
TIM
DATE 11-May-2006
=1ms). This is
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